Application for U.S. Pat., Ser. No. 584,686, filed on June 6, 1975, which is a continuation-in-part of Ser. No. 487,826, filed on July 12, 1974 as well as application for U.S. Pat., Ser. No. 598,527, filed on July 23, 1975, which is a continuation-in-part of Ser. No. 541,900, filed on Jan. 1, 1975 now abandoned, all of which are incorporated herein by reference, describe and claim substituted 4-alkoxy and 4-benzyloxypyrazolium compounds, and methods of use thereof for the control of broadleaf weeds, grass weeds and of plant pathogenic fungi.
The key intermediates for the preparation of the above-identified herbicidal and fungicidal pyrazolium compounds are represented by a 3,5-diphenyl-4-pyrazolol compound of formula: ##SPC1##
Wherein R.sub.1 hydrogen or a C.sub.1 -C.sub.6 straight chain or branched alkyl.
Hitherto, formula (I) 4-pyrazolol intermediates have been prepared by various known processes, which though suitable for preparations on a laboratory scale are not satisfactory for the preparation of said compounds in large quantities. These processes, hereinbelow briefly described, utilize relatively expensive starting materials, such as 1,3-diphenyl-1,3-propanedione, or hazardous materials such as p-toluenesulfonylazide. Further, said processes which utilize a plurality of steps yield the desired formula (I) 3,5-diphenyl-4-pyrazolols only in low yields.
Thus M. J. Nye and W. P. Tang [Tetrahedron, 28, 1152 (1952)] describe the preparation of a formula (I) pyrazolol wherein R.sub.1 is methyl, comprising condensing 2-acetoxy-1,3-diphenyl-1,3-propanedione, with methylhydrazine followed by hydrolysis of the acetyl group, as hereinbelow illustrated: ##SPC2##
The intermediate 2-acetoxy-1,3-diphenyl-1,3-propanedione itself is prepared from 1,3-diphenyl-1,3-propanedione by bromination to obtain the 2-bromo analog and subsequent replacement of the bromo group with acetoxy. See R. de Neufville and H. V. Pechmann. Chem. Berichte 23, 3325 (1890).
Nye and Tang also describe in Can. J. of Chem. 48, 3563 (1970) the preparation of 3,5-diphenyl-4-pyrazolol by the following routes:
A. Condensation of 1,3-diphenylpropanetrione (prepared from 1,3-diphenyl-1,3-propanedione) with hydrazine;
B. Condensation of 2-acetoxy-1,3-diphenyl-1,3-propanedione (prepared from 1,3-diphenyl-1,3-propanedione as hereinabove described) with hydrazine followed by alkaline hydrolysis;
C. Condensation of chalcone epoxide with p-toluenesulfonylhydrazide, followed by oxidation with chromium trioxide (20% yield); or
D. Condensation of 1,3-diphenyl-2-propanone with p-toluenesulfonylazide in the presence of sodium ethoxide (45% yield).
As hereinabove mentioned, these processes utilize relatively expensive starting materials (A and B) or hazardous materials (C and D) or the products are obtained in low yields (C and D), thus rendering the above processes unattractive.